indexOf and lastIndexOf String Methods

When you want to search inside one string for another string, JavaScript gives us two great methods - indexOf and lastIndexOf.

[rotrose]

We can always learn something new and special from you, the last indexOf example is excellent. Thank you.

[yolismazacarias]

Thank you so much for explaining these concepts. I have a better understanding of them now!

[johnywhy]

i believe a common use of the `Start Position` parameter is to find successive instances of the same item:

L=console.log

{
const sSentence = 'Be the change that you want to see.'
const sChar = 'e'
let aFound = FindItems(sSentence, sChar)
L(aFound)

function FindItems(sSentence, sChar)
{
let iFound, iStart, aFound = []
do
{
iFound = sSentence.indexOf(sChar, iStart)
if (iFound > -1) {
aFound.push(iFound)
iStart = iFound + 1
}
}
while (iFound > -1)
return aFound
}
}

But, would array.Filter be faster than this?

[TiffanyNg]

it's nice to know that we have LastIndexOf(), but I'm more curious When we will use it in real life? maybe soemthing like searching for latest input or so?

[kikevanegazz]

Hi. First of all... thanks for the video. It was pretty clear. Now, my question is... as a programmer yourself, which scenarios have you had to use them?

[ripplesr]

Thank you very much man!
can u plz tell me how the second parameter starts to look for the specified words when it comes down to lastIndexOf("string", 15) for instance?

[hindj]

what about lastIndexOf with the second parameter?

[johnywhy]

i realized in JS, both negative and positive numbers are truthy, and 0 is falsey. I can understand why indexOf returns -1 for not-found. It can't return 0, cuz that's a legitimate array-index.

Still, it seems somehow inappropriate for indexOf to return -1, since it's a nonsensical array-index, and -1 is truthy. Wondering if there's another value that would be more appropriate, like null, or undefined, or false?

[japeter]

Why would you store console.log() in a variable?

[amitgarg]

Very nice explanation but please improve sound quality. It's very low

[holo]

Can someone explain this?
let x = ["Python", "C++", "C", "Java"];
let z = x.lastIndexOf("C", 1);
and its -1.... How??

[kodama]

Entendi como usarlo aunque esta en ingles el audio